The ability to make calls! Oh Snap! lol I kid I kid...In all seriousness I honestly don't know what else they could add, maybe more space? higher MP camera (even though 5 is way more than enough for my needs. I honestly don't know.

I think 4G would be awesome for 2011, since it would slowly be building up around the world by then.
Also, Apple should make a Dock Connector to HDMI adapter so you can hook the iPhone 4/5 up to your TV and play HD videos/other content (the iPhone 4 already has the capability; the VGA adapter can put out up to 720p on it).
More megapixels (while increasing the image quality) would be awesome, along with a real Xenon flash.
64 gigs.

BTW: I think Apple should leave the processor speed at 1Ghz, but make the "A5/A4 II" dual-core and push developers to use GCD. That would make it much more awesome to use, because it could actually handle heavy operations (and real multitasking) with ease.